Potent Greenhouse Gas More Common in Atmosphere Than Estimated

WASHINGTON, Oct. 23 /PRNewswire-USNewswire/ -- New research indicates a
powerful greenhouse gas is at least four times more prevalent in the
atmosphere than previously estimated. The research, based on data from a
NASA-funded measurement network, examined nitrogen trifluoride, which is
thousands of times more effective at warming the atmosphere than an equal mass
of carbon dioxide.
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Using new analytical techniques, Ray Weiss of the Scripps Institution of
Oceanography in La Jolla, Calif., led a team of researchers in making the
first atmospheric measurements of nitrogen trifluoride. The amount of the gas
in the atmosphere, which could not be detected using previous techniques, had
been estimated at less than 1,200 metric tons in 2006. The new research shows
the actual amount was 4,200 metric tons. In 2008, about 5,400 metric tons of
the gas are in the atmosphere, a quantity that is increasing at a rate of
about 11 percent per year.

"Accurately measuring small amounts of nitrogen trifluoride in air has proven
to be a very difficult experimental problem, and we are very pleased to have
succeeded in this effort," Weiss said. The research will be published Oct. 31
in the American Geophysical Union's Geophysical Research Letters.

Emissions of nitrogen trifluoride were thought to be so low that the gas was
not considered a significant potential contributor to global warming. It was
not covered by the Kyoto Protocol, the 1997 agreement to reduce greenhouse gas
emissions signed by 182 countries. The gas is 17,000 times more potent as a
global warming agent than a similar mass of carbon dioxide. It survives in the
atmosphere about five times longer than carbon dioxide. However, current
nitrogen trifluoride emissions contribute only about 0.15 percent of the total
global warming effect caused by current human-produced carbon dioxide
emissions.

Nitrogen trifluoride is one of several gases used during the manufacture of
liquid crystal flat-panel displays, thin-film solar cells and microcircuits.
Many industries have used the gas in recent years as an alternative to
perfluorocarbons, which also are potent greenhouse gases, because it was
believed that no more than two percent of the nitrogen trifluoride used in
these processes escaped into the atmosphere.

The Scripps team analyzed air samples gathered during the past 30 years,
including samples from the NASA-funded Advanced Global Atmospheric Gases
Experiment network of ground-based stations. The network was created in the
1970s in response to international concerns about chemicals depleting the
ozone layer. It is supported by NASA as part of its congressional mandate to
monitor ozone-depleting trace gases, many of which also are greenhouse gases.
Air samples are collected at several stations around the world. The Scripps
team analyzed samples from coastal clean-air stations in California and
Tasmania for this research.

The researchers found concentrations of the gas rose from about 0.02 parts per
trillion in 1978 to 0.454 parts per trillion in 2008. The samples also showed
significantly higher concentrations of nitrogen trifluoride in the Northern
Hemisphere than in the Southern Hemisphere, which the researchers said is
consistent with its use predominantly in that hemisphere. The current observed
rate of increase of nitrogen trifluoride in the atmosphere corresponds to
emissions of about 16 percent of the amount of the gas produced globally.

In response to the growing use of the gas and concerns that its emissions are
not well known, scientists recently have recommended adding it to the list of
greenhouse gases regulated by Kyoto.

"As is often the case in studying atmospheric emissions, this study shows a
significant disagreement between 'bottom-up' emissions estimates and the
actual emissions as determined by measuring their accumulation in the
atmosphere," Weiss said.

For more information about NASA and agency programs, visit:

http://www.nasa.gov

SOURCE NASA

Steve Cole, NASA Headquarters, Washington, +1-202-358-0918,
stephen.e.cole@nasa.gov; Robert Monroe/Mario Aguilera, Scripps Institution of
Oceanography, La Jolla, Calif., +1-858-534-3624, scrippsnews@ucsd.edu